Infrared vision systems can be utilized in vehicles such as cars and trucks to improve driver vision at night and in rain, fog and snow. Such an infrared vision system typically includes a receiver for detecting infrared radiation received from a scene and a monitor for displaying an image of the detected scene. The amount of contrast between different portions of the displayed image is based upon the amount of detectible difference in the intensity of the infrared radiation received from the corresponding portions of the scene. Indicia appearing on traffic signs and the like can be difficult (if not impossible) to discern within the displayed image because the contrast between the indicia and the adjacent portions of the image is so low, i.e., the amount of radiation detected by the infrared receiver from the indicia and from surrounding portions of the sign is about the same. The invention addresses this problem.